Parasitism rate of Plutella xylostella (Lepidoptera: Plutellidae) larvae in greenhouse by Tetrastichus howardi (Hymenoptera: Eulophidae) females at different densities.

ABSTRACT

Parasitoids control insect pests, but their number per host affects their efficiency. The objective of this work was to evaluate the best density of Tetrastichus howardi (Olliff, 1893) (Hymenoptera Eulophidae) individuals parasitizing fourth instar Plutella xylostella (Linnaeus, 1758) (Lepidoptera Plutellidae) larvae in greenhouse conditions. These larvae were exposed to parasitism by T. howardi females with 11, 31, 61, 91, 121, 151 and 181 parasitoid/host ratios with 10 replications during 96 hours. After this period the larvae were kept on host plants (Brassica oleracea) until pupa formation. Tetrastichus howardi parasitized and reproduced in P. xylostella larvae at all its densities tested, but with higher values, 84% and 10 ± 2.4 individuals, respectively, with 91 parasitoids/host. Nine T. howardi females per P. xylostella larvae are the adequate number to manage this insect pest.